I think it's more that people handle stress differently and many people in vet school aren't accustomed to not being able to keep up in classes. I think based on meeting people and reading what people put on these forums that a lot of people go into vet school expecting to love it and having it be fun, and then are pretty surprised that it's a hellhole and shocked that they can't study a moderate amount and get the grades they used to get while riding their horse daily/playing IM soccer/partying all weekend/whatever their pastime is. At Davis people failed our first pchem exam and the professors talked to them, assigned them tutors - this is obviously not a unique thing to have happen in this class and the people before us got through it and so will my current classmates.
It sucks to study a ton and then get a bleh grade, but it's all a matter of perspective in the end. My perspective is that I've met a few really dumb vets and I always figure that if they can get through it, then any of us can. Eventual Eventer is currently laughing at me for this perspective, damn her
tldr: do your best, you'll still be a vet in the end.